"Over the past 150 years, vocal cord, or glottic cancer, has been almost exclusively a disease associated with smoking and almost entirely seen in patients over 40 years old," explained study senior author Dr. Steven Zeitels. He directs the Division of Laryngeal Surgery at Massachusetts General Hospital in Boston.

"Today, nonsmokers are approaching 50 percent of glottic cancer patients, and it is common for them to be diagnosed under the age of 40," Zeitels said in a hospital news release. "This epidemiologic transformation of vocal cord cancer is a significant public health issue."

In the study, the researchers examined the records of 353 patients treated for vocal cord cancer at the Massachusetts Eye and Ear Infirmary and Massachusetts General Hospital (MGH) between July 1990 and June 2018.

None of the 112 patients treated from 1990 to mid-2004 were 30 or younger, but 11 of the 241 patients treated from 2004 to 2018 were 30 or younger, including three who were aged 10 to 19. Only three of those 11 patients were smokers.

Analysis of tumor tissue samples revealed from 10 of the 11 patients who were 30 and younger showed that all them had high-risk strains in HPV, which also causes cervical cancer and other types of cancers.

Though the study did not prove that HPV caused these vocal cord cancers, the increase appears to resemble an earlier rise in cases of throat cancer, which was also linked with infections with high-risk strains of HPV, the researchers said.

Zeitels and his colleagues first noted an increase in vocal cord cancers among nonsmokers about 15 years ago, and initially attributed that rise to increased travel and exposure to infectious diseases. But they then decided to investigate the role that HPV infection might play in vocal cord cancer in younger nonsmokers.

"Large-scale studies are now needed to determine the pace of the increase in glottic cancer among nonsmokers, the incidence of high-risk HPV in these cancers, and changes in the age and genders of those affected," Zeitels said.

The study was published Feb. 7 in a special supplement in the March issue of the Annals of Otology, Rhinology and Laryngology.